The present invention relates to a press roll, especially a substitute for a paper machine roll made of granite, and to a method for manufacturing the same.
During the manufacture of paper, pulp or wet web of paper is pressed and dehydrated as it is continuously passed between a bottom press roll and a top press roll while placed on felt material. A rubber roll is generally used as the bottom press roll which is brought into contact with the felt material. However, the top press roll is directly contacted with the wet paper for excerting high load, and is thus required for the special features below:
(1) Good release property from the paper PA1 (2) Resistance to high loads PA1 (3) Smooth surface PA1 (4) Less deformation of the roll not to break the paper when the wet paper is pressed.
A top press roll made of granite called a stone roll shows good release property from paper. However, since the granite is a natural material, variation in the quality is great, and much labor and time are required for forming the granite into rolls. The production period of large rolls is especially unstable due to difficulties in obtaining large granite. The granite roll is further disadvantageous in that impacts tend to cause scars. As an alternative, a paper machine roll is known which contains stone powder such as quartz sand in hard rubber. Although this type of top press roll is advantageous in that the elongation is large and the cost is lower, the release property from the paper is insufficient and the separation of the stone powder during use accelerates roughness on the surface.